1. Field of the Invention
The present invention relates to a system and method for network communication. Specifically, this invention relates to a system and method for using a protocol extension to separate data path from control path.
2. Description of Related Art
Various network systems are currently available, many of which are combined to create larger integrated systems. Many network systems use differing communication methods and protocols. During data read and write operations standard protocols typically communicate data packets and control packets across the same communication path. For example, in the industry standard Small Computer Systems Interface (SCSI) over Remote Direct Memory Access (RDMA) protocol (SRP) definition, the SRP command, its corresponding RDMA operations, and the corresponding SRP response, must all be transferred via the same RDMA channel, that is, going through the same q-pairs of the nodes involved in the RDMA and SRP communications. Therefore, the CPU issuing the SRP command and the memory containing the data to be transferred must be located on the same node.
SCSI is one of the most common interfaces used to request block storage services for current networks. SCSI is a client-server architecture and a SCSI transport maps the client-server SCSI protocol to a specific interconnect. One such SCSI transport is Internet SCSI, or iSCSI. iSCSI is a mapping of the SCSI remote procedure call over the TCP protocol.
The SCSI layer builds and receives SCSI CDBs (Command Descriptor Blocks) and passes/receives them and their parameters to/from the iSCSI layer. The iSCSI layer builds/receives iSCSI PDUs (Protocol Data Unit) and relays them to/from one or more TCP connections. One or more TCP connections that link an initiator with a target form a session. Connections within a session are identified by a CID (connection ID). Sessions are identified by the SID (session ID). For any iSCSI request issued over a TCP connection, the corresponding response and/or other PDUs must be sent over the same connection. This is called command connection allegiance. Thus, if an initiator sends a READ command, the target must send the requested data and the status to the initiator over the same TCP connection that was used to deliver the SCSI command. iSCSI presents the same restriction as SRP.
iSCSI Extensions for RDMA (iSER) provides an RDMA capability to iSCSI by layering iSCSI on top of Remote Direct Memory Access Protocol (RDMAP). RDMAP permits data to be transferred directly in and out of buffers without intermediate data copy operations.
The restrictions inherent in these systems can strain a system designer's ability to place the control path and data path functionality on distinct network nodes, which may be useful for scaling performance and/or simplifying synchronization/coherent protocol. These and other deficiencies exist in current network systems, therefore, a solution to these and other problems is needed to provide a network system capable of transmitting data information and command information over separate data paths to separate nodes within the network.